In on-board electrical systems of vehicles, the problem arises that they have a fixed voltage limit. The voltage limit represents a maximally permissible voltage value for the voltage in the on-board electrical system. If the actual voltage in the on-board electrical system exceeds the predefined voltage limit, the actual voltage may be short-circuited or otherwise limited so as to keep to the voltage limit in the on-board electrical system.
If, however, during braking of the vehicle, voltages above the voltage upper limit are produced by way of operation in generator mode, for safety reasons those voltages are often short-circuited or otherwise limited, with the result that they cannot be used for recharging of an accumulator or a battery. Vehicles that use those on-board electrical systems therefore have a high fuel consumption.